GitHub Actions: Check URLs using lychee

[Calinou]

This makes it possible to be aware of dead links and replace them with other resources (such as archived versions) as soon as possible.

Note that class reference URLs not checked within this repository, as I plan to also integrate lychee into godotengine/godot's CI (which has the source of the class reference files).

Note

CI will fail until we resolve #10674, so that we remove the download.tuxfamily.org links from the docs.

[tetrapod00]

Approve the idea. Shader function replacement links are correct.

Can't review the lychee action implementation

[skyace65]

I rebased this PR since tetrapod's PR was merged and now the URL check is failing on a different link. I'm not sure why though because the link works for me.

[Calinou]

I rebased this PR since tetrapod's PR was merged and now the URL check is failing on a different link. I'm not sure why though because the link works for me.

I've added gamedevartisan.com to exclusions. Some websites tend to block link checkers and will return various error codes (typically 429, but sometimes 403 or even 503 in this case).

[skyace65]

@mhilbrunner I'd like your review before merging this since it's adding another check

[mhilbrunner]

I think something like this is a good idea, and I didn't spot anything in the workflow. Looks good to me!

Some things can be expanded, but I think we want to see this in action first & iterate. So, lets go ahead.

[mhilbrunner]

Thank you!

[brotheramai]

@Calinou
This action has been failing since 2025. Perhaps github updated in a way that broke compatibility? Here's a sample of the failure output:

Run lycheeverse/lychee-action@v2
Run echo "$HOME/.local/bin" >> "$GITHUB_PATH"
Run # Remove any existing lychee binary to prevent conflicts
Run # Create a temporary directory for downloads and extraction
Downloading from: https://github.com/lycheeverse/lychee/releases/download/lychee-v0.23.0/lychee-x86_64-unknown-linux-gnu.tar.gz
Extracting lychee-x86_64-unknown-linux-gnu.tar.gz
lychee
docs/
docs/README.md
docs/TROUBLESHOOTING.md
docs/lychee.1
docs/PRE_COMMIT.md
Run # Install lychee from the temporary directory
Run /home/runner/work/_actions/lycheeverse/lychee-action/v2/entrypoint.sh
error: invalid value '.' for '--base ': Error with base dir . : Base must either be a URL (with scheme) or an absolute local path. See --help for more information. If you want to resolve root-relative links in local files, also see --root-dir.

For more information, try '--help'.

[Calinou]

@brotheramai Thanks for the reminder! I've opened a PR to fix this:

• Fix Lychee URL checking on CI #11993

There is still one outstanding error I didn't manage to fix though.